The controlled movement of air has become a problem of major significance to modern buildings and structures of all types. For example, heating and air cooling systems require the controlled circulation of air through a building, and pollution and other air quality equipment requires the sealed transfer ducting of gases and dust-laden air through a controlled filter network. In any air movement system one or more blowers or fans may be found at some point or points along the circulation path. Frequently, in long ducting paths, it becomes necessary to insert supplementary booster fans into the ductwork in order to maintain continuous air flow at a specified level.
Fans and other air movements devices have not changed significantly over the years, although design improvements have led to units which move air more efficiently and at controlled volume flow rates.
In any application involving movement of air through closed ducting systems, provision must be made for the installation and removal of suitable fans and blowers. These installations are preferably made in a manner which provides easy access to the moving parts so that such parts may be readily cleaned, repaired or maintained. Prior art devices have accomplished this result by structuring blower enclosures and assemblies having hinged doors with removable blower and motor assemblies. For example, U.S. Pat. No. 3,425,621, issued Feb. 4, 1969, discloses an inline centrifugal fan with a hinged door, wherein the fan and motor assembly is attached to the door for swingable movement relative to the enclosure. When the door is closed the fan is swung into position adjacent an inlet opening and is ready to operate. When the door is open the entire assembly swings away from the enclosure for maintenance or other purposes. If the blower or motor is to be replaced the assembly must be unbolted from the hinged door and removed. This patent also discloses an alternative embodiment wherein the fan is mounted internal the enclosure and the motor is mounted external the enclosure and coupled to the fan via a belt. The same principle is used with this structure, i.e. the fan and motor are attached to a hinged door for access purposes.